Conventionally, in warehousing load transport systems, a plurality of running routes are provided for the electrically driven cargo carriers in relation to load storage sections of the shelves at each level. Therefore, the cargo storage efficiency of shelves becomes low if the vertical distances between the upper and lower running routes at different levels are too big compared to the height of the load to be handled. On the other hand, the carrier running route at each level requires a number of power supply wires and control signal transmission wires for operating the electrically driven cargo carriers. When floor plates are provided between two opposing assemblies of shelves at each level story for such carrier running routes, the power supply wires and control signal transmission wires can be laid horizontally on the floor plates, parallel with each other. However, when floor plates are not provided between two opposing assemblies of shelves at each level, the power supply wires and control signal transmission wires have to be laid one over the other in parallel at each level on the sides of the carrier running routes.
Accordingly, it is an object of the invention to enhance the cargo storage efficiency of shelves by economizing the vertical space required for power supply wires and control signal transmission wires disposed one over another in parallel to reduce the vertical intervals between the carrier running routes at two levels by as much as possible.
In addition, in the cargo transport system of the prior art in which running routes for the cargo carriers are provided at each storage shelf level, if the cargo carrier is relatively high, such as may be necessitated by its drive system, the vertical space required for the running carrier takes up a substantial portion of the total height of the facility, such as that of the shelves. This means that a load storage efficiency of the shelves becomes low, and makes the overall cost of the warehousing facilities expensive.
Accordingly, another object of the present invention is to sharply reduce the number of cargo carriers in relation to the number of levels of shelves for load storage.